1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to allocating channel time for communication between wireless devices in a wireless PAN (Personal Area Network). More particularly, the present invention relates to an apparatus and method for allocating channel time for each application in a single superframe when applications such as wireless USB and IEEE 802.2, which are implemented in a MAC layer, coexist on a wireless PAN.
2. Description of the Related Art
Due to the progress of digital technology, many digital products such as DVD players, cable STBs (SetTop Boxes), DVCRs (Digital Video Cassette Recorders), DTVs (Digital TVs) and PCs (Personal Computers) are interconnected on a single network. Various protocols can be implemented in such equipment in order to transmit or receive AV data to or from other equipment. When these various protocols are to be transmitted in a wireless PAN (Personal Area Network), a method of sharing a wireless medium is required.
FIG. 1 is a diagram showing the channel time allocation structure of a superframe that a related art piconet coordinator (PNC) generates. Referring to FIG. 1, the channel time allocation (CTA) structure is divided into two layers. An upper layer shows the time-based structure of continuous frames of an upper application layer, and a lower layer shows the time-based structure of a superframe of a MAC layer for wireless communication. It is noted that “application” as used in the specification refers to interfaces or standards and “application layer” as used in the specification does not refer to the application layer in the Open Systems Interconnect (OSI) Model. The upper application layer is configured such that data are directly transmitted from the upper application layer without the MAC layer in existing wired communication. In the case of wireless communication, the data are transmitted from the upper application layer through the lower MAC layer and the received data are transferred back to the upper application layer through the lower MAC layer. That is, the structure shown in FIG. 1 can be obtained by combining an upper application layer used in existing wired communication with a MAC layer required in wireless communication.
According to such a structure, isochronous transaction should be transmitted every frame for applications having a very short frame period, e.g., a wireless USB device. Further, if a large CTA (CTA #6) is allocated from another device, data cannot be transmitted during this period. Thus, the data in this period should be buffered. Furthermore, since the size of the buffer-generating CTA is not determined, it is impossible to know how much buffer is needed for a device. In addition, if the superframe duration is not coincident with a multiple of the frame size, this also acts as a factor hindering periodic transmission. In an example of FIG. 1, since the frame #9 is a broken frame, it cannot normally transmit data related thereto.